NMF-Based spectral unmixingof herschel observations of the horsehead nebula

摘要

The HIFI instrument, onboard the Herschel space observatory, provides hyperspectral observations with unprecedented angular and spatial resolution in the far-infrared. In this paper, we present hyperspectral observations of the [CII] line (the fine structure line of ionized carbon) at 1900 GHz (158 μm), of the famous Horsehead nebula. In order to analyze the data we propose a method to decompose them into a limited and comprehensive set of components. The method uses nonnegative matrix factorization (NMF) to extract latent spectral endmembers in the data. The number of needed endmembers is obtained using an estimate of the noise power derived from the data. A Monte-Carlo scheme is used to estimate the optimal endmembers and the error-bars. Finally, the maps of linear coefficients are reconstructed using non-negative least squares. Using this method, we find two components in our data which we relate to the dynamic structure of the nebula: the Horsehead is evaporating.